1. Field of the Invention
This invention relates to two speed power tools and clutches in general and two speed powered wrenches in particular.
It is generally recognized that it is desirable for powered wrenches to have a high speed/low torque mode and a low speed/high torque mode. The high speed/low torque mode is used to quickly engage a threaded bolt to a nut or other structure until the bolt is seated while the low speed/high torque mode is used to tighten the bolt. The high speed/low torque mode significantly reduces the amount of time required to engage and tighten a bolt. This is important in assembly line operations where such a time saving may have dramatic cost reduction impact.
The shift from the high speed to low speed mode is generally accomplished by a clutch mechanism. The present invention provides an improved clutch in combination with such power tools.
2. Description of the Prior Art
A powered wrench of the general type herein discussed having a high speed/low torque and low speed/high torque mode is taught by U.S. Pat. No. 3,696,871 issued to Stenbacka on Oct. 10, 1972. Stenbacka teaches a clutch having two rims, each of which have teeth. The rims are moveable with respect to one another so that a mode change is effected by engaging or disengaging the teeth from one another.
Clutches are also used in power tools for disengaging the wrench portion of such tools when an overload or predetermined torque is reached. A spring clutch is used for such a purpose in U.S. Pat. No. 3,956,905 issued to Thackston on May 18, 1976, and in U.S. Pat. No. 3,370,680 issued to Bangerter, et al, on Feb. 27, 1968.
Although the clutches used in two speed powered wrenches, such as that taught by Stenbacka, have generally been effective, the present invention represents an improvement. Through the use of a simpler design utilizing fewer parts, lower cost, greater reliability, faster action, and a longer service life is achieved.